1. Field of the Invention
This invention relates to an adjustable leveling suspension unit for vehicle shock absorbers having a coil compression spring, the leveling unit being intended to compensate for spring sag and to allow for leveling the vehicle height.
2. Description of the Prior Art
Suspension systems for vehicles include hydraulic telescopic dampers and coil spring combinations in a variety of arrangements. In one form of suspension system the load supporting coil spring is fitted over the damper body to abut on a sleeve which is angularly and axially movable on the damper body, all as seen in Savory U.S. Pat. No. 2,756,045 of July 24, 1956. A somewhat similar arrangement can be found in Nicholls U.S. Pat. No. 3,618,927 of Nov. 9, 1971.
Means limited to accommodating the heighth of the vehicle frame relative to the road surface for purposes of leveling the vehicle frame is seen in Hans Hagi Switzerland Pat. No. 283,288 of Sept. 16, 1952.
The prior art includes examples of MacPherson suspension arrangements having fixed supports for the coil springs as seen in MacPherson U.S. Pat. No. 2,624,592 of Jan. 6, 1953, and MacPherson U.S. Pat. No. 2,660,449 of Nov. 24, 1953. More recent examples are Pacis et al U.S. Pat. No. 4,260,176 and Pflughaupt et al U.S. Pat. No. 4,260,177, both of Apr. 7, 1981.
Other examples in the prior art are Arlasky U.S. Pat. No. 3,603,575, Thompson et al U.S. Pat. No. 4,036,335, Nicholls U.S. Pat. No. 4,079,922, and Keijzer et al U.S. Pat. No. 3,954,257.
The problem with the prior art is that the correction for spring sag or fatigue requires overcoming high-friction loads in very restricted areas. Also, the systems that do provide for adjustment are quite limited in the amount of correction that can be obtained. Furthermore, a major problem in adjustable devices is the high-friction loads which are present and which require great torque effort to make adjustments, usually in a tight or restricted area.